<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>应用算术运算符计算商品金额</title>
<script >
   var price=19.7;  //定义单价
   var number=100; //定义数量
   var sum=price*number;
   window.alert(sum);
   document.write("<h1> this is a heading </h1>");



</script>
</head>
<body>

</body>
</html>